June i6, 1923 
Watery~Roi of Tomato Fruits 
897 
Tabi.:^ I .—Results of inoculating tomato fruits with the Oospora associated with watery-rot 
Green. 
Rip¬ 
ening. 
Ripe. 
Total. 
Fruits inoculated. 
Fruits infected. 
Green. 
Ripening. 
Ripe. 
j Total. 
Num¬ 
ber. 
Per 
cent. 
Num¬ 
ber. 
Per 
cent. 
Num¬ 
ber. 
Per 
cent. 
i 
Num¬ 
ber. 
Per 
cent. 
Pricked. 
Unpricked. 
160 
16 
90 
7 
27 
5 
277 
28 
I18 
0 
0 
64 
0 
71 
0 
26 
a 2 
96 
0 
208 
0 
75 
0 
® Infected through the stem scar. 
Although these infections were obtained v/ith an apparently pure 
culture of Oospora, the possibility of contamination by Bacillus caroto- 
vorus was not overlooked. The cultures were repeatedly plated and 
examined microscopically for the presence of bacteria but no evidence 
of bacterial contamination was found in either the plates or microscopic 
mounts. Moreover, the fungus pricked into halved potato tubers caused 
only a slight superficial growth, even when allowed to stand for a con¬ 
siderable period of time, while B. carotovorus produced a very decided 
rot (PI. 4, B). The infections of the inoculated tomato fruits were 
therefore unquestionably caused by the fungus. 
The stems and leaves of 15 vigorous tomato seedlings about 4 inches 
tall were thoroughly sprayed with the Oospora spores and kept in a 
moist chamber 60 to 72 hours but no infections developed. Ten similar 
tomato seedlings were thoroughly pricked in stems and leaves and 
smeared with the spores of Oospora, but the fungus was unable to invade 
the tissues. It therefore seems to have little if any parasitic action on 
tomato plants. 
MORPHOLOGY OP PUNGUS 
The Oospora causing watery rot of tomato fruits consists of a hyaline, 
septate mycelium with granular contents and numerous short branches 
arising near the septa at an angle of about 45® from the main filament 
(PI. 3, A) and other longer branches of a two-or-three-forked type (PI. 
3 , B-D). 
The hyphae vary from 2.5 to 7.5 /z in diameter. The younger branches 
are narrower than the main filament but the taper is very gradual. 
Reproduction is accomplished by the breaking up of the hyphae into 
their cells which serve as spores. The branches shown in Plate 3, A, 
divide into numerous short cells which round at the ends (PL 3, E, F, H) 
and separate. The rounding appears to begin in the apical cells (PI, 
3, G), but occurs in all cells of a branch almost simultaneously. At a 
certain stage of their development these cells appear to be chains of 
spores arising from the main part of the mycelium (PI. 3, E, F), but 
by the time they lose their coherence, or shortly afterward, the main fila¬ 
ment itself breaks up by cell division and separation into numerous cells 
of different lengths, which round at the ends, and when short are often 
indistinguishable from those formed from the lateral branches. They 
are hyaline and granular and are capable of germinating immediately. 
The transverse diameter of these sporelike ceils (oidia), which for con¬ 
venience will be referred to hereafter as spores, varies from 2.5 to 7.5 /i; 
the length from 3.2 to 40 fx and in some cases even to more than 60 ju. 
